Hey everyone!

Here are our meeting logs:

http://meetbot.debian.net/tor-meeting/2023/tor-meeting.2023-03-09-15.58.html

And our meeting pad:

Anti-censorship --------------------------------

Next meeting: Thursday, March 16 16:00 UTC

Weekly meetings, every Thursday at 16:00 UTC, in #tor-meeting at OFTC (channel is logged while meetings are in progress)

== Goal of this meeting ==

Weekly check-in about the status of anti-censorship work at Tor. Coordinate collaboration between people/teams on anti-censorship at the Tor Project and Tor community.

== Links to Useful documents ==

* Our anti-censorship roadmap: * Roadmap: https://gitlab.torproject.org/groups/tpo/anti-censorship/-/boards * The anti-censorship team's wiki page: * https://gitlab.torproject.org/tpo/anti-censorship/team/-/wikis/home * Past meeting notes can be found at: * https://lists.torproject.org/pipermail/tor-project/ * Tickets that need reviews: from sponsors, we are working on: * All needs review tickets: * https://gitlab.torproject.org/groups/tpo/anti-censorship/-/merge_requests?sc... * Sponsor 28 * must-do tickets: https://gitlab.torproject.org/groups/tpo/-/milestones/10 * possible-do tickets: https://gitlab.torproject.org/groups/tpo/-/issues?scope=all&utf8=%E2%9C%... * Sponsor 96 * https://gitlab.torproject.org/groups/tpo/-/milestones/24 * Sponsor 139 <-- hackerncoder, irl, joydeep, meskio, emmapeel working on it * https://pad.riseup.net/p/sponsor139-meeting-pad

== Announcements ==

== Discussion ==

* No news yet about the inclusion of snowflake-02 in Orbot, after asking at S96 meeting. * the are asking meskio by email privately, but he didn't answer being in vacation, will do today

* What is the procedure for creating a new repository under https://gitlab.torproject.org/tpo/anti-censorship ? Do I need to ask someone to create a repository or can I just do it? * dcf wants to move other repositories there: * https://gitlab.torproject.org/dcf/extor-static-cookie * https://gitweb.torproject.org/pluggable-transports/goptlib.git * It should be possible to just create new repos. * dcf will try it, and report back if there's trouble.

* Resynchronization with Upsteamed Remove HelloVerify countermeasure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...) * Syncing with upstream will require dropping one version of golang from CI, are we okay with that? * https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf... "The only problem I'm having with this is that it no longer builds with go1.15 due to the x/crypto dependency update. Is it possible to keep the old version or perhaps rebase these changes off of the versions of pion/dtls and pion/webrtc that we currently have pinned rather than the master branches?" * go1.15 is the version in current Debian stable (bullseye), go1.19 is available in backports. go1.19 will be the version in the next stable (bookworm) coming in a few months.

== Actions ==

* move the ampcache snowflake fallback forward

== Interesting links ==

*

== Reading group ==

This paper is about detecting Tor-in-obfs4 when you only have a traffic sample; e.g., you only get to look at every 100th packet that passes through a router that handles both obfs4 and non-obfs4 flows. Traffic sampling means you cannot use features like "look at the first n packets of a flow" or "compare the timing of two consecutive packets". Instead, you can only look at aggregate statistical features and have to be memory-efficient. The system collects 12 statistics (Table III in the appendix) and stores them in a data structure called a nest count Bloom filter (NCBF), which essentially is just a composition of 12 counting Bloom filters (https://en.wikipedia.org/wiki/Counting_Bloom_filter). The statistics are things like "number of non-empty upstream packets" (C₂) and "number of downstream packets with payload length between 62 and 465" (C₁₁). From these 12 statistics, they derive 14 features (mostly ratios of statistics) and feed them to a random forest classifier. For evaluation they use a 15-minute sample of backbone traffic provided by a third party, MAWI (https://mawi.wide.ad.jp/mawi/ditl/ditl2019-G/201904090000.html) and insert their own self-collected obfs4 traffic into it. They say the detection has few false negatives (finds almost all obfs4 bridges), but too many false positives to be usable directly for blocking decisions; they mention the need for "secondary testing" of suspected bridges.

* We will discuss "Detecting Tor Bridge from Sampled Traffic in Backbone Networks" on March 9 * https://www.ndss-symposium.org/wp-content/uploads/madweb2021_23011_paper.pdf * https://www.youtube.com/watch?v=kL7YCRer3To&list=PLfUWWM-POgQvGOVAk1HjP3... * Questions to ask and goals to have: * What aspects of the paper are questionable? * Are there immediate actions we can take based on this work? * Are there long-term actions we can take based on this work? * Is there future work that we want to call out in hopes that others will pick it up?

== Updates ==

Name: This week: - What you worked on this week. Next week: - What you are planning to work on next week. Help with: - Something you need help with.

cecylia (cohosh): last updated 2023-03-02 Last week: - Lox tor browser integration work in progress - https://gitlab.torproject.org/tpo/anti-censorship/team/-/issues/116 - Finished getting the wasm client integrated as a Tor Browser module This week: - continue Lox tor browser integration - find a better way to generate and call wasm client in tor-browser-build - make team repos for Lox pieces - expand client-side support for more Lox features - continue work on conjure client-side recovery Needs help with:

dcf: 2023-03-09 Last week: - drafted snowflake-01 bridge update for February 2023 https://opencollective.com/censorship-circumvention/projects/snowflake-daily... - attended 2023-03-04 relay operators meetup and answered questions about snowflake https://lists.torproject.org/pipermail/tor-relays/2023-March/021080.html - documented further sporadic blocking of cdn.sstatic.net in some networks in Iran https://gitlab.torproject.org/tpo/anti-censorship/team/-/issues/115#note_288... - made a graph of users in Russia since Tor Browser 12.0.3 and the Hello Verify mitigation; curiously it increased users in snowflake-02 but not snowflake-01 https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf... - noticed that conntrack changes did not persist after a reboot on the snowflake bridges, and started an experiment to measure the effect https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf... Next week: - migrate goptlib to gitlab https://gitlab.torproject.org/tpo/anti-censorship/team/-/issues/86#note_2823... (for real) Help with:

meskio: 2023-03-09 Last week: - catch up (or fail to) after vacation - deploy and break bridgedb (bridgedb#40064) - test bridges without ORPort public (rdsys#154) - review nil pointer fix in webtunnel (webtunnel!5) - coordinate the update of pion libraries and snowflake in debian, including the HelloVerify patch Next week: - rdsys fixes to use onbasca (rdsys#153)

Shelikhoo: 2023-03-09 Last Week: - [Merge Request Awaiting] Add SOCKS5 forward proxy support to snowflake (snowflake!64) - [Research] HTTPT Planning https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/httpt... - WebTunnel @ TorBrowser mobile(https://gitlab.torproject.org/tpo/applications/tor-browser-build/-/merge_req...) - Upstreaming Remove HelloVerify countermeasure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...) - Fix return nil error on unrecognized request http upgrade failure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtu...) - Research on dynamic bridge DOL in china(https://gitlab.torproject.org/tpo/anti-censorship/connectivity-measurement/l...) - meta: fill the "donate" link on addons.mozilla.org (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...) - consider propagating 2FA everywhere, maybe at the April Tor Meeting (https://gitlab.torproject.org/tpo/tpa/team/-/issues/41083#note_2884138) - Review Proxy: add an option to bind to a specific address (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...) - Resynchronization with Upsteamed Remove HelloVerify countermeasure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...) Next Week: - [Research] WebTunnel planning (Continue) - Try to find a place to host another vantage point - Fix return nil error on unrecognized request http upgrade failure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/webtu...) - Resynchronization with Upsteamed Remove HelloVerify countermeasure (https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowf...) onyinyang: 2023-03-09 Last week: - Working on distributor backend for Lox server (integration with rdsys) - enabling Lox server to communicate with rdsys through rdsys-backend-api This week: - Continuing work on Lox server integration with rdsys - Reconfigure Lox Bridgeline to fit with Tor's bridge info - Figure out the proper multithreading in Rust to add bridges to Lox's bridgedb - (later) Consider a reasonable approach for bridge groupings for Lox buckets

Itchy Onion: 2023-03-08 Last week: - Finished most of issue #40252 (Standalone proxy outbound address) (!136) - Worked on issue #40252 (NAT probetest for standalone proxy) - Started looking at #40231 (Client sometimes send offer with no ICE candidates) This week: - Add warning message if the user provided IP address is not used by proxy to establish WebRTC connection (issue #40252 !136). In my testing, sometimes the IP obtained from Pion's selectedCandidatePair is not accurate. I chatted with Pion dev and think there might a bug in Pion. But from my testing it only happens on the first peerconnecion so not a huge problem for us. - Closed issue #40252 (NAT probetest for standalone proxy) - Working on #40231 (Client sometimes send offer with no ICE candidates). My current understanding is that this shouldn't happen. There was a similar issue but is fixed and merged: https://github.com/pion/webrtc/issues/1143. Doing more research on it. hackerncoder: 2023-03-09 last week: Next week: - getting ooni-exporter to work with torsf (snowflake) - ooni-exporter web_connectivity - work on "bridgetester"? - how does iran block bridges

cece: 2022-12-22 This week: - working on creating a dummy WhatsApp bot Next week: - My bot is not yet working as expected s? still trying to figure that out Help with: - resources